Outstanding!
I'm a long time user and fan of "bag flasks" for field use. In that light I'll pass along an insight that adds to the utility of this one.
The longish spout and plug will help it orient in the bag butt-down with the outside curve of the horn to the bottom of a gusseted bag that's on the order of 6-7" wide, my typical size. In that position the horn is in perfect orientation to grab and pour with no shuffling and repositioning in the hand. If horns get too short relative to the width of the bag, they want to stand on their butt. Too long and their spouts stick out of the bag. If there's a rule of thumb I can discern, overall horn length around the curve including plug is best at 2-3" longer than the width of the bag, as this appears to be.
Just one more way of saying beauty aside, you nailed it on functionality.